my mate is my enemy

everyone finds thier mate at the age of 18 but im 25 and still havent found her one faithful but destructive day i found her on accident.The night walkers were about to attack but waiting for the order but whos order and then I smelled her the sweet intoxicating smell I found in the woods.But when I saw her everything changed cause I knew what my alpha wanted me to do.She was the leader of our biggest enemy.The night walkers.What will he do will he kill her or try to save her either one was going to be hard and destructive.